Alternatives to the Global Warming Potential for Comparing Climate Impacts of Emissions of Greenhouse Gases

The Global Warming Potential (GWP) is used within the Kyoto Protocol to the United Nations Framework Convention on Climate Change as a metric for weighting the climatic impact of emission of different greenhouse gases. Here, two metrics are proposed, which are based on a simple analytical climate model. The first metric is called the Global Temperature Change Potential model and represents the temperature change at a given time due to a pulse emission of a gas (GTPp); the second is similar but represents the effect of a sustained emission change model (GTPs). Both GTPp and GTPs are presented as relative to the temperature change due to a similar emission change of a reference gas, carbon dioxide.

Different grazing management strategies change greenhouse gas emissions and global warming potential in global grasslands

This paper discusses the impact on climate change of hydrofluorocarbons (HFCs) in fire suppression applications. Alternatives and substitutes for HFCs, perfluorocarbons (PFCs), and ozone depleting substances (ODSs) have recently been extensively evaluated. NFPA 2001 defines a clean fire extinguishing agent as an electrically non-conducting, volatile, or gaseous fire suppressant that does not leave a residue upon evaporation. A clean agent must have no known effect on the ozone layer and also, no effect on any human survival within an enclosure protected by a clean agent, and in normally occupied areas must be used in a concentration that is less than “no observed adverse effect level (NOAEL)”. NOAEL is a measure of clean agent toxicity to humans under test conditions. The HFCs that are projected for large volume use have global warming potentials (GWPs) lower than the replacing ODSs. GWPs of HFCs replacing ODSs ranges from 120 to 12,000 as per the year 2000 data of Intergovernmental Panel on Climate Change (IPCC). HFC-23 with a GWP of 12,000 is used as a replacement for ODSs to a very limited extent. However, there are relatively large emissions of HFC-23 from the HCFC-22 manufacturing process. However, the majority of HFCs have GWPs much lower than that of HFC-23. NFPA 2001 standard demonstrates the fact that the GWP value considered by itself does not provide an indication of the impact of fire extinguishing clean agent on climate change. Further, the paper briefly describes the clean agent fire extinguishing system design considerations to extinguish fires either by flame extinguishment or by inerting in accordance with the changing characteristics of fire hazard scenarios in building and industrial occupancies. An important finding of this brief study is that the value of 0.4858 kg/m3 is a total flooding factor for HFC-227ea fire extinguishing agent representing the quantity of halocarbon clean agent required to achieve a selected design fire extinguishing concentration of 6% at a specified ambient temperature of 21 °C. It is further important to understand that the impact of a fire extinguishing clean agent on climate change is a function of both the GWP of the gas and the amount of gas emitted. For example, carbon dioxide has one of the lowest GWP values of all greenhouse gas emissions (GWP = 1), yet emissions of CO2 account for approximately 85% of the impact of all greenhouse gas (GHG) emissions. The characteristics of fire hazard scenarios with respect to anticipated fires have been continuously changing in India due to emerging trends in the up gradation/modern furnishing and interior design considerations/requirements in almost all the urban, semi-urban, and rural occupancies. The data from IPCC and Asia Pacific Fire Magazine, October 25, 2011 showed that if nothing changes, the HFC emissions are likely to be equivalent to between 9 and 19% of global greenhouse gas emissions by 2050, which indicates that the impact of HFC fire extinguishing clean agents on climate change is minuscule. As a result, HFCs are expected to remain viable, sustainable, and environmentally acceptable replacements for Halon 1301, which was phased out due to ozone depletion potential problems under Montreal and other protocols.

Methane emissions along biomethane and biogas supply chains are underestimated

Core Ideas Elevated O3 (EO3) effects on GHG flux and GWP from O3‐sensitivity wheat systems were studied.EO3 reduced belowground biomass of O3‐sensitive (SW) and O3‐tolerant (TW) wheat cultivars.O3‐sensitivty of wheat cultivar affected responses of gaseous C and N emission and GWP to EO3.SW wheat would release more freshly assimilated C, adding GHG emission and GWP under EO3. The effects of elevated O3 (EO3) on greenhouse gas (GHG) emissions and global warming potential (GWP) from wheat systems with differential O3 sensitivity are not well understood. The nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions from cropping (CP) and bare soil or root‐free (BS) plots, GWP, GWP per unit yield, and biomass and its allocation to belowground between O3‐sensitive (cultivar YN19) and tolerant (cultivar Y15) wheat (Triticum aestivum L.) systems were investigated at EO3 and ambient O3 (AO3) with an open‐air O3 fumigation system. Results indicated that a 50% elevation above AO3 significantly reduced belowground biomass of the two cultivars. The EO3 significantly increased the cumulative emissions of CO2 and N2O but did not change that of CH4 in YN19 CP. For BS, it significantly increased the emission of CO2 but decreased that of CH4 and N2O. The EO3 significantly increased the GWP and GWP per unit yield in YN19 CP but reduced the GWP in BS. The O3 sensitivity of wheat cultivar affected the responses of gaseous C and N emission, GWP and GWP per unit yield to EO3. The O3‐sensitive wheat cultivar would release more freshly assimilated C, increasing cumulative GHG emissions, GWP and GWP per unit yield in response to O3 stress, when compared to the O3 O3‐tolerant wheat cultivar. Our results suggest that EO3 may impair soil C and N sequestration in an O3 O3‐sensitive wheat–soil system in view of lower root biomass but higher CO2 and N2O emissions under EO3.

Cost-effective reductions of non-CO 2 greenhouse gases

Organic matter content increases in soil with no-tilled permanent raised beds (PBs) compared with soil with conventionally tilled beds (CBs), and this might affect greenhouse gas (GHG) emissions. Greenhouse gas (CO2, N2O, and CH4) emissions were measured from PBs, from which crop residue was either removed or retained and from CBs where crop residue was retained. The CO2 emission was not affected by tillage, but CH4 and N2O emissions were lower in PBs when residue was retained than in CBs. Removing crop residue from PBs reduced CO2 emissions compared with when it was retained, but it had no effect on N2O and CH4 emissions. The global warming potential (GWP) of GHG emissions was higher in CBs (801 kg CO2/ha/year) than in PBs (517 kg CO2/ha/year) with crop-residue retention, but more C was sequestered in the 0–60 cm soil layer in PBs (83.4 Mg C/ha) than in CBs (79.2 Mg C/ha). Crop-residue removal in PBs had little effect on the GWP of GHG compared with PBs with crop residue retained, but less C was sequestered in the latter (63.1 Mg C/ha). Net GWP (considering soil C sequestration, GHG emissions, fuel used, glyphosate application, fertilizer and seed production) was lower in CBs with crop-residue retention (1062 kg CO2/ha/year) than in PBs with crop-residue removal (6,120 kg CO2/ha/year), but it was larger than in PBs with crop-residue retention (−681 kg CO2/ha/year). We found that reduced tillage when beds were made permanent and crop-residue retention greatly reduced net GWP compared with when beds were tilled and remade each year.We found that retention of crop residue in PBs increased the emission of CO2 compared with where it was removed, but tillage did not affect fluxes of CO2. Emission of CH4 and N2O was larger from CBs than from PBs, but crop-residue management in PBs had no significant effect on fluxes of CH4 and N2O. Concentrations of mineral N were larger in CBs than in PBs, whereas the removal of crop residue from PBs increased mineral N concentration. Soil temperature was higher in CBs than in PBs and in PBs with crop residue retained compared with where it was removed. Soil water was better preserved in PBs than in CBs and in PBs where residue was retained than where it was removed. The higher water content in the PB compared with the CB will favor plant growth during dry spells. However, retaining crop residues in PBs will require sufficient application of inorganic N, as mineral N in soil is lower in PBs than in CBs or PBs with crop residue removed. Limited N availability in PBs with crop residue retained might reduce yields as poor farmers in the central highlands of Mexico apply little or no N fertilizer. Reduced tillage on PBs and crop-residue retention strongly reduced the net GWP of the system compared with the case when beds were remade each year. PBs with residue retention reduced net GWP by 50% compared with CBs with residue retention, but the removal of residues from the PBs more than doubled it.

Enhancing resource use efficiency of alfalfa with appropriate irrigation and fertilization strategy mitigate greenhouse gases emissions in the arid region of Northwest China

This addendum contains 2 important messages. (1) This document supersedes all previous versions of this work. Please do not use any older versions any more. (2) The atmospheric-science community now believes that it cannot estimate confidently the ''Global Warming Potentials'' (GWPs) of the indirect effects of greenhouse gases. A GWP is a number that converts a mass-unit emission of a greenhouse gas other than CO{sub 2} into the mass amount of CO{sub 2} that has an equivalent warming effect over a given period of time. This report refers to GWPs as ''CO{sub 2}-equivalency factors.'' For example, a forthcoming report by the Intergovernmental Panel on Climate Change disavows many of the GWPs estimated in an earlier IPCC report, and states that GWPs for the indirect effects of the non-CO{sub 2} greenhouse gases cannot be estimated accurately yet. However, this does not mean that in principle there are no GWPs for the non-CO{sub 2} greenhouse gases; rather, it means that some of the GWPs are uncertain, and that the earlier IPCC estimates of the GWPs may or may not turn out to be right (albeit, in at lease one case, discussed in this paper, the earlier estimates almost certainly will be wrong). In this report the author used the IPCC's 1990 estimates of the GWPs for 20-, 100-, and 500-year time horizons, and expressed the bottom-line results for each of these three time horizons. However, the recent uncertainty about the GWPs affects how you should interpret the results. Because the IPCC has disclaimed some of its GWPs, the GWPs as a group no longer are the best estimates of the warming effects over 20, 100, and 500 years. Instead, they are just a collection of possible values for the GWPs--in short, scenarios. Therefore, you should interpret the ''20-, 100-, and 500-year time horizons'' as three general GWP scenarios--say, scenarios, A, B, and C.--and not as time-period scenarios. For example, you should not think that the results shown here under the ''100-year time horizon'' actually embody the scientific community's best estimates of the relative warming potentials of the various greenhouse gases over a 100-year period. Instead, you should understand the results to be the outcome of making a particular set of assumptions about what the GWPs might be. The ''time horizons'' no longer necessarily represent time horizons, but rather general scenarios for, or assumptions about, the GWPs.

<p>Biochar is a carbon-rich black stable solid substance that when utilized as soil amendment can effectively mitigate greenhouse gas (GHG) emission. However, during the pyrolysis process of organic feedstock (i.e. manure) greenhouse gases are released as the feedstock undergo thermochemical degradation. Many studies were reported with regards to the effectiveness of biochar to mitigate greenhouse gas emission and to maintain soil quality via carbon sequestration. However, no clear investigation was done regarding biochar utilization on reducing GHG emission in an integrated perspective that starts from pyrolysis (production) to field application (utilization). To evaluate the integrated influence of biochar utilization on the overall Global Warming Potential (GWP) and (Greenhouse Gas Intensity) GHGI at different temperature, the fluxes of GHGs during feedstock pyrolysis to soil application were calculated. The key components include GHGs released during production processes and biogenic GHG emissions taking place in the soil via short-term incubation experiment in lowland and upland condition treated with biochar pyrolyzed at different temperature. Highest pyrolysis temperature of 700<sup>o</sup>C emitted 6.92 Mg CO<sub>2</sub>-eq ton<sup>-1</sup> biochar, wherein 8.7% and 91.2% was contributed by Carbon dioxide (CO<sub>2</sub>) and Methane (CH<sub>4</sub>) effluxes, respectively, during pyrolysis. This GHG emission during pyrolysis at 700<sup>o</sup>C was 5.6, 2.2, and 1.5 times higher than at 400<sup>o</sup>C, 500<sup>o</sup>C and 600<sup>o</sup>C, respectively. Meanwhile, biochar produced at lowest temperature (Biochar400) when utilized as soil amendment emitted 43.4 and 38.2 Mg CO<sub>2</sub>-eq ha<sup>-1</sup> in lowland and upland condition, respectively. In addition, this emission value under lowland (and upland) condition was 1.38 (1.36), 1.51 (1.56) and 1.86 (1.91) times higher than Biochar500, Biochar600 and Biochar700, respectively. Combining the GWP during the production and the utilization processes in lowland and upland condition reveal that at 400<sup>o</sup>C emanates the lowest overall GWP of 93.3 and 88.1 Mg CO<sub>2</sub>-eq ha<sup>-1</sup>, respectively.  Moreover, under lowland (and upland) condition, overall GWP at 400<sup>o</sup>C was noted to be 65.7% (71.7%), 131.6% (140.4%) and 221.9% (237.1%), lower than at 500<sup>o</sup>C, 600<sup>o</sup>C and 700<sup>o</sup>C, respectively. In conclusion, the use of lower temperature during biomass pyrolysis and utilization of its derived biochar could be a practical approach to mitigate GHG emissions.</p><p> </p><p>Keywords: Biochar, Pyrolysis, Greenhouse gas, Methane, Global warming potential, Greenhouse gas intensity</p>

The impact of organic fertilizer replacement on greenhouse gas emissions and its influencing factors

Better information on greenhouse gas (GHG) emissions and mitigation potential in the agricultural sector is necessary to manage these emissions and identify responses that are consistent with the food security and economic development priorities of countries. Critical activity data (what crops or livestock are managed in what way) are poor or lacking for many agricultural systems, especially in developing countries. In addition, the currently available methods for quantifying emissions and mitigation are often too expensive or complex or not sufficiently user friendly for widespread use.The purpose of this focus issue is to capture the state of the art in quantifying greenhouse gases from agricultural systems, with the goal of better understanding our current capabilities and near-term potential for improvement, with particular attention to quantification issues relevant to smallholders in developing countries. This work is timely in light of international discussions and negotiations around how agriculture should be included in efforts to reduce and adapt to climate change impacts, and considering that significant climate financing to developing countries in post-2012 agreements may be linked to their increased ability to identify and report GHG emissions (Murphy et al 2010, CCAFS 2011, FAO 2011).

Major US electric utility climate pledges have the potential to collectively reduce power sector emissions by one-third

Biochar is widely used in agriculture to enhance crop yield, improve soil fertility, and regulate greenhouse gas (GHG) emissions. Its effectiveness, however, depends not only on its properties but also on soil moisture conditions, making integrated water management essential for maximizing its benefits. The study reports the results of a laboratory incubation experiment using three biochar application rates (0, 20, and 40 t ha−1) and two irrigation regimes—flooded irrigation and alternate wetting and drying (AWD)—to investigate the effects of biochar amendment and water management on soil greenhouse gas (GHG) emissions. The results indicated that there was no significant interaction between biochar and water regulation on GHG emissions, and changes in soil moisture and biochar application levels had no significant impact on carbon dioxide (CO2) emissions. Compared to flooded irrigation, AWD effectively enhanced soil microbial activity, increasing nitrous oxide (N2O) emissions by 62.50% to 88.35%, but significantly reducing methane (CH4) emissions by 44.30% to 68.55%, thereby lowering the soil’s global warming potential (GWP). Additionally, biochar amendment significantly increased soil SOC and TN contents, enhanced soil enzyme activities, and significantly improved microbial carbon use efficiency (CUE), the C/N ratio, and the net nitrification rate (NNR). However, it had no significant effect on soil N2O and CO2 emissions, while significantly suppressed CH4 emissions. Throughout the entire growth period, biochar application increased soil GWP overall. However, during the first water cycle, GWP increased with higher biochar application rates, whereas in the second water cycle, biochar application exhibited a suppressive effect on GWP. In conclusion, integrating biochar application with AWD irrigation can optimize soil CUE, enhance soil nutrient supply, and mitigate, to some extent, the potential increase in GHG emissions induced by biochar. This provides valuable insights for carbon management and sustainable agricultural development.

Increasing reactive nitrogen (N) input has been recognized as one of the important factors influencing climate system through affecting the uptake and emission of greenhouse gases (GHG). However, the magnitude and spatiotemporal variations of N-induced GHG fluxes at regional and global scales remain far from certain. Here we selected China as an example, and used a coupled biogeochemical model in conjunction with spatially explicit data sets (including climate, atmospheric CO2 , O3 , N deposition, land use, and land cover changes, and N fertilizer application) to simulate the concurrent impacts of increasing atmospheric and fertilized N inputs on balance of three major GHGs (CO2 , CH4 , and N2 O). Our simulations showed that these two N enrichment sources in China decreased global warming potential (GWP) through stimulating CO2 sink and suppressing CH4 emission. However, direct N2 O emission was estimated to offset 39% of N-induced carbon (C) benefit, with a net GWP of three GHGs averaging -376.3±146.4Tg CO2 eqyr(-1) (the standard deviation is interannual variability of GWP) during 2000-2008. The chemical N fertilizer uses were estimated to increase GWP by 45.6±34.3Tg CO2 eqyr(-1) in the same period, and C sink was offset by 136%. The largest C sink offset ratio due to increasing N input was found in Southeast and Central mainland of China, where rapid industrial development and intensively managed crop system are located. Although exposed to the rapidly increasing N deposition, most of the natural vegetation covers were still showing decreasing GWP. However, due to extensive overuse of N fertilizer, China's cropland was found to show the least negative GWP, or even positive GWP in recent decade. From both scientific and policy perspectives, it is essential to incorporate multiple GHGs into a coupled biogeochemical framework for fully assessing N impacts on climate changes.